Wave Forces on a Submerged Bridge Deck with a Box Girder Situated over a Step Bottom

Abstract

During hurricanes or typhoons, wave forces acting on low-lying coastal bridges can cause significant damage to their decks. However, current research has paid little attention to the impact of topography on wave forces. This paper aimed to propose an analytical model based on potential flow theory to analyze the impact of topography on wave forces on bridge decks. The model employs the eigenfunction-matching method to solve the boundary value problem of waves acting on bridge decks over a step bottom. The validity of the model was confirmed by comparing it with published hydrodynamic experiment results. We also examined the effect of the truncation order on wave forces and selected a proper truncation order. The wave forces on the bridge deck located ahead or behind the bottom step were calculated. This study examined the water depth, distance from the bottom step to the bridge deck, and coastal boundary on wave forces. The calculated results indicate that the coastal boundary would significantly influence wave forces on bridge decks, especially for long-period incident waves. The wave forces can be mitigated by an optimized configuration of the wave–structure–topography system. This paper contributes to understanding the impact of topography on wave forces acting on bridge decks during extreme wave conditions and provides insights into optimizing the design of coastal bridges. The proposed analytical model can supply preliminary guidance at the initial stage of bridge design without costly numerical simulations or physical model tests.